This article offers an analysis of the right to equality recognized in Article 3 of the German Basic Law, in dialogue with the jurisprudence of the Federal Constitutional Court. In contrast to a reduced view of the principle of equality as a simple mandate for equal treatment, it proposes a reading that conceives of it as a dual or double rule: one that imposes an obligation to treat equally those in equivalent situations, and another that requires differential treatment when circumstances justify it. This conception allows a better understanding of the structure of the right to equality as a principle that does not prohibit all inequality, but only that which is arbitrary or unjustified. In this sense, the article analyzes how this dual dimension of the principle of equality affects the application of the proportionality test, particularly in the weighing phase, where the interests at s...